The present invention relates to a communication apparatus applied to a wireless network and a method thereof, and more particularly, to a method of controlling a communication mechanism utilized to arbitrate transmissions of a first wireless signal corresponding to a first wireless standard and a second wireless signal corresponding to a second wireless standard, and a communication apparatus utilizing the method.
In present wireless communication systems, in order to sufficiently utilize advantages of different wireless techniques, such as Bluetooth, WiFi or WiMAX, several wireless techniques are integrated in a single communications device. For example, Bluetooth and WiFi techniques are implemented in a mobile phone or PDA in a voice over wireless area network (VoWLAN) to transmit voice signals and data. However, since Bluetooth and WiFi signals both work at the frequency band 2.4-2.48 GHz, there will be interference between them when they are put to use simultaneously in the VoWLAN. To solve this problem, mechanisms utilized to arbitrate transmissions of different wireless signals that may cause interference to each other when transmitted/received are developed. Packet traffic arbitration (PTA) is a conventional mechanism often adopted to solve the coexistence problem of Bluetooth and WiFi. In brief, the PTA mechanism controls the transmission of WiFi signal. That is, it arbitrates and decides whether to let the WiFi module to send out the WiFi signal immediately or to block and delay the transmission of WiFi signal generated by the WiFi module. Therefore, Bluetooth and WiFi transmissions are interlaced in the time domain and will not generate interference to each other. Because the PTA mechanism is fully detailed in the 802.15.2 specification, detailed introduction of the PTA mechanism is omitted for the sake of brevity.
As those of ordinary skill in the art will readily appreciate, in the wireless network, when the signal quality is poor or the packet size is large, an access point will apply the Request to Send/Clear to Send (RTS/CTS) mechanism before sending packets to prevent hidden node effect. That is, when the access point wants to send a packet to a mobile station, it first sends an RTS packet to the mobile station, and the mobile station broadcasts a CTS packet after receiving the PTS packet. Only when the access point receives the CTS packet can it send the data packet. However, when the PTA mechanism and the RTS/CTS mechanism are both active, the mobile station may not be able to send the CTS packet promptly since the PTA mechanism controls the transmitting authority of the mobile station. In a situation where both the Bluetooth and the WiFi modules ask permission to send packets at the same time, the Bluetooth packet will be sent immediately while the transmission of the WiFi packet will be delayed because of the higher transmission priority assigned to Bluetooth packets. Therefore, if the WiFi module is going to send the CTS packet to the access point, the delay may cause the CTS packet to fail to reach the access point in time, and when the access point cannot receive the CTS packet from the station during a specific time period (i.e. 10 μs), the WiFi connection between the access point and the mobile station is given up, and a disconnection event (de-authentication or disassociation) is sent to the mobile station. In this situation, the user will hear an apparent voice mute. The voice mute may last for a significant period of time because the security mechanism of the wireless network will obstruct the instant reconnection of the mobile station.